This invention relates to devices for the extraction of cartridges containing a substance for the preparation of a beverage which are designed to be fitted to the extraction head of a conventional espresso machine.
Ordinarily, espresso type coffee machines are used to extract ground coffee which has been measured out and placed beforehand in a metal filter held in a receptacle.
The upper part of espresso type coffee machines consists of a spray nozzle for spraying the coffee, a tightening ring for fixing the receptacle and a rubber seal designed to ensure fluid tightness and good extraction by forcing the water to pass through the layer of coffee.
However, the use of this system is laborious and causes soiling and frustration because the quality of the beverage obtained does not always live up to expectations. This is because it is difficult to measure out the coffee correctly and to determine whether it has been properly ground.
The use of coffee capsules, for example those according to Swiss Patent No. 605 293, is a good alternative because handling is simplified, the quality of the coffee is better and constant and the risk of soiling is reduced. Nevertheless, the use of coffee capsules requires perfect compatibility between the capsule and the extraction system, essentially for reasons of fluid tightness and to force the water through the layer of coffee.
This compatibility may be embodied in the design of the machine although, in this case, the machine generally allows the use of capsules only.
European Patent No. 70 403 relates to an espresso machine with an adapter for the extraction of open cartridges made of filter paper which is fluid-tight in its medial part. However, this system is restricted to one type of capsule which is difficult to produce.